Frequency-domain haptic waveform compensation for haptic transducers

Abstract

A method for minimizing post-playback oscillation during playback of a haptic playback waveform to a haptic transducer may include determining whether a frequency response of the haptic playback waveform has a notch with a notch frequency at approximately a resonant frequency of the haptic transducer and, responsive to the notch frequency differing from the resonant frequency, modifying the haptic playback waveform for playback to the haptic transducer by shifting the notch frequency to approximately the resonant frequency.

What is claimed is: 
     
       1. A method for minimizing post-playback oscillation during playback of a haptic playback waveform to a haptic transducer, comprising:
 determining whether a frequency response of the haptic playback waveform has a notch with a notch frequency at approximately a resonant frequency of the haptic transducer; and 
 responsive to the notch frequency differing from the resonant frequency, modifying the haptic playback waveform for playback to the haptic transducer by shifting the notch frequency to approximately the resonant frequency. 
 
     
     
       2. The method of  claim 1 , further comprising, responsive to an absence of a notch in the frequency response of the haptic playback waveform, modifying the haptic playback waveform for playback to the haptic transducer by applying a notch filter at approximately the resonant frequency to the haptic playback waveform. 
     
     
       3. The method of  claim 1 , further comprising responsive to the notch frequency being approximately equal to the resonant frequency, playing back the haptic playback waveform without modification to the haptic transducer. 
     
     
       4. The method of  claim 1 , wherein the shifting of the notch frequency to approximately the resonant frequency comprises:
 determining a time scaling factor as a ratio between the notch frequency and the resonant frequency; and 
 time scaling the haptic playback waveform by the time scaling factor, such that the haptic playback waveform as modified v T (t)=v R (ct), where v R (t) defines the haptic playback waveform without modification as a function of time, and c is the time scaling factor. 
 
     
     
       5. The method of  claim 1 , wherein the shifting of the notch frequency to approximately the resonant frequency further comprises applying an amplitude compensation factor to compensate the haptic playback waveform as modified such that a depth of the resulting notch in the frequency response of the haptic playback waveform as modified is approximately equal to the depth of the notch in the frequency response of the haptic playback waveform prior to modification. 
     
     
       6. A system for minimizing post-playback oscillation during playback of a haptic playback waveform to a haptic transducer, comprising:
 one or more inputs for receiving information regarding a resonant frequency of the haptic transducer; and 
 a processing subsystem configured to:
 determine whether a frequency response of the haptic playback waveform has a notch with a notch frequency at approximately the resonant frequency of the haptic transducer; and 
 responsive to the notch frequency differing from the resonant frequency, modify the haptic playback waveform for playback to the haptic transducer by shifting the notch frequency to approximately the resonant frequency. 
 
 
     
     
       7. The system of  claim 6 , the processing subsystem further configured to, responsive to an absence of a notch in the frequency response of the haptic playback waveform, modify the haptic playback waveform for playback to the haptic transducer by applying a notch filter at approximately the resonant frequency to the haptic playback waveform. 
     
     
       8. The system of  claim 6 , the processing subsystem further configured to, responsive to the notch frequency being approximately equal to the resonant frequency, play back the haptic playback waveform without modification to the haptic transducer. 
     
     
       9. The system of  claim 6 , wherein the shifting of the notch frequency to approximately the resonant frequency comprises:
 determining a time scaling factor as a ratio between the notch frequency and the resonant frequency; and 
 time scaling the haptic playback waveform by the time scaling factor, such that the haptic playback waveform as modified v T (t)=v R (ct), where v R (t) defines the haptic playback waveform without modification as a function of time, and c is the time scaling factor. 
 
     
     
       10. The system of  claim 9 , wherein the shifting of the notch frequency to approximately the resonant frequency further comprises applying an amplitude compensation factor to compensate the haptic playback waveform as modified such that a depth of the resulting notch in the frequency response of the haptic playback waveform as modified is approximately equal to the depth of the notch in the frequency response of the haptic playback waveform prior to modification. 
     
     
       11. A mobile device, comprising:
 a haptic transducer; and 
 a haptic control subsystem configured to:
 determine whether a frequency response of a haptic playback waveform has a notch with a notch frequency at approximately the resonant frequency of the haptic transducer; and 
 responsive to the notch frequency differing from the resonant frequency, modify the haptic playback waveform for playback to the haptic transducer by shifting the notch frequency to approximately the resonant frequency. 
 
 
     
     
       12. The mobile device of  claim 11 , the haptic control subsystem further configured to, responsive to an absence of a notch in the frequency response of the haptic playback waveform, modify the haptic playback waveform for playback to the haptic transducer by applying a notch filter at approximately the resonant frequency to the haptic playback waveform. 
     
     
       13. The mobile device of  claim 11 , the haptic control subsystem further configured to, responsive to the notch frequency being approximately equal to the resonant frequency, play back the haptic playback waveform without modification to the haptic transducer. 
     
     
       14. The mobile device of  claim 11 , wherein the shifting of the notch frequency to approximately the resonant frequency comprises:
 determining a time scaling factor as a ratio between the notch frequency and the resonant frequency; and 
 time scaling the haptic playback waveform by the time scaling factor, such that the haptic playback waveform as modified v T (t)=v R (ct), where v R (t) defines the haptic playback waveform without modification as a function of time, and c is the time scaling factor. 
 
     
     
       15. The mobile device of  claim 14 , wherein the shifting of the notch frequency to approximately the resonant frequency further comprises applying an amplitude compensation factor to compensate the haptic playback waveform as modified such that a depth of the resulting notch in the frequency response of the haptic playback waveform as modified is approximately equal to the depth of the notch in the frequency response of the haptic playback waveform prior to modification.